Linear engines comprise electric machines, capable of converting electric energy to mechanical energy in the form of translation movement, preferably axial movement (along an imaginary axis).
By this way, and differently from rotary engines, linear engines are capable of producing linear movement with no need for mechanical couplings such as belts, clutch assemblies, and similar devices. In this regard, a linear engine comprises a static (fixed) portion and dynamic (moving) portion.
According to specialized literature, functioning of a linear engine is analogous to the functioning of a rotary engine, where an electromagnetic force (generated by interaction between a current applied to the engine coil and a magnetic field) shifts the engine dynamic (or moving) portion in relation to the engine static (or fixed) portion.
Among possible designs of linear engines known from the state of the art, it can be cited a linear engine which static (or fixed) portion thereof includes three iron cores (wherein only a central core has a coil) and the dynamic (or moving) portion consists of three permanent magnets disposed between said iron cores.
This design can also be implemented in linear compressors where displacement of dynamic (or moving) portion of linear engine is functionally associated with the piston (which is reciprocately moved inside a piston, thereby compressing a working fluid).
Example of a linear engine-based linear compressor is disclosed in BR Patent Application PI 0401581-9. This document refers to a linear engine comprising a stator (containing a concentrically arranged core and coil) and a cursor, wherein said cursor is secured (even indirectly) to the compressor carcass, and said cursor is functionally associated with the compressor piston. More specifically, said stator is formed by an outer ring (coil) and an inner ring (ferrous core), wherein both are indirectly fixed to the compressor carcass by suspension means. With regard to the linear engine cursor, which is located between the outer ring and inner ring of the stator, same is formed by a magnet ring integrated into a support guide (which is also associated with the piston). Further, in accordance with this document, it is observed that said cursor may physically contact the outer face of the stator core.
Another example of a linear engine-based linear compressor is described in BR Patent Application PI 9801434-0, which focus on a linear engine structure itself, which improves engine efficiency and simplifies assembling of a lamination (set of “C”-shaped metal blades), whereby said lamination is attached by a fixation ring and not by a welding process. According to this document, a linear engine includes lamination wherein protruding portions respectively comprise a groove formed by concentric circles of radially disposed iron parts, a connector for coil wires and a non-magnetic fixation ring disposed at the groove to prevent said iron parts from being loosened.
Although said BR Patent Applications No. PI 0401581-9 and PI 9801434-0 comprise mere examples of linear engines (for linear compressors) pertaining to the state of the art, it should be noted that most linear engines (for linear compressors) are basically similar, at least conceptually, to the referred to examples.
That is, most linear engines (for linear compressors) already known from the state of the art comprise an essential design based on stator of concentric rings and cursor located between the concentric rings of the stator. It is also observed that most linear engines (for linear compressors) have its coil wound by metal laminations (juxtaposed laminar metal sheets).
Furthermore, it is also known that most linear engines (for linear compressors) are indirectly attached to the compressor carcass by means of suspensions and the like, or also by means of the block itself that defines a compression cylinder.
These two conventional aspects observed in linear engines (for linear compressors) can be construed as aspects capable of being improved because:
Forming of metal laminations for winding coils, in addition to rendering electric insulation of the assembly unsafe, a complex productive forming and mounting method is required.
Fixation of a linear engine to a compressor carcass (by the means cited above), in addition to making electric insulation of the assembly unsafe, it may cause structural damages to other compressor parts, such as, for example, a block that defines a compression cylinder.
Within the context explained above, it should be noted that there is a need for developing a linear engine for linear compressor which does not present such drawbacks and which is capable of being improved.